Slotted airfoil ultra high frequency antenna



A. DORNE SLOTTED AIRFOIL ULTRA HIGH FREQUENCY ANTENNA Filed July 31, 1958 2 Sheets-Sheet 1 IN VENTOR. #877102 Dom/E BY AMA, .emA A Aug. 16, 1960 A. DORNE 2,949,606

SLO'ITED AIRFOIL ULTRA HIGH FREQUENCY ANTENNA Filed July :51, 1958 2 Sheets-Sheet 2 i l/ i 1:! IN VENTOR. AHTHUR Doe/v5 SLO'ITED AIRFOIL ULTRA HIGH FREQUENCY ANTENNA Arthur Dome, Glen Head, N.Y., assignor to Dome and iarlgolim Inc., Westbury, N.Y., a corporation of New Filed July 31, 1958, Ser. No. 752,299

14 Claims. (Cl. 343-708) This invention relates to ultra high frequency antennas, and more particularly to such antennas, suitable for use on vehicles moving at high velocities, and which are mechanically strong, compact in size and with good electrical characteristics over a broad frequency band of operation.

Many problems are encountered in the design of antennas for use on vehicles travelling at high velocities, such as aircraft moving at speeds of the order of twice the speed of sound or higher. Such antennas should be of maximum structural strength to withstand any mechanical stresses and should also be of minimum size in order to reduce the aerodynamic drag on the vehicle. In addition to the foregoing mechanical requirements, such antennas should also have desirable electrical characteristics, such as a uniform radiation pattern over a broad range of frequencies of operation, broad band width, and a low standing wave ratio.

In antennas according to the present invention, a number of novel features are utilized to enable the antenna to achieve all of the aforementioned desired characteristics. These features include the use of a blade-type vertically polarized antenna with metallic shunt feed elements on opposite sides of a metallic main radiator element. Such an arrangement provides for substantially all-metal leading and trailing edges for the antenna which greatly increases its strength at high speeds. The main radiator element is also rigidly fastened directly to the surface of the vehicle by a structurally strong metallic connection without the use of any intermediate insulation and the shunt feed elements are insulated from the surface of the vehicle at only small areas to further increase the structural strength of the antenna.

To insure proper electrical characteristics, the antenna is preferably of top-loaded design with a slot cut in the top portion of the main radiator element to provide for proper distribution of the antenna currents. This arrangement, in conjunction with the shunt feeding, provides for an antenna which has a broad bandwidth of operation, symmetrical radiation pattern and low standing wave ratio.

It is therefore an object of this invention to provide an antenna suitable for use on vehicles moving at high velocities which is both compact in size and structurally strong.

Yet another object of this invention is to provide an antenna for use on vehicles moving at high velocities, the main radiator element of which is mounted directly on the surface of the vehicle without the use of any intermediate insulation.

It is a further object of this invention to provide an antenna of this type which possesses the electrical characteristics of wide bandwidth of operation, uniform radiation pattern and a low standing wave ratio.

It is another object of this invention to provide a blade antenna which has a length of less than a quarter wave length at the frequency of operation, but is still mechanically strong and maintains electrical characteristics of 2,949,606 Patented Aug. 16, 1%60 wide bandwidth, uniform radiation pattern and low standing wave ratio.

Other objects and advantages of htis invention will become more apparent upon consideration of the following specification and annexed drawings, in which:

Fig. 1 shows a side elevational view of one form of antenna according to the present invention, attached to the vehicle;

Fig. 2 shows front elevational view of the leading edge of the antenna of Fig. 1;

Fig. 3 shows an enlarged sectional side elevation view of the antenna taken along 'line 3-3 of Fig. 2;

Fig. 4 shows a fragmentary sectional plan view of one of the antenna slots taken along line 44 of Fig. 3;

'Fig. 5 shows a bottom plan view of the base of the antenna of Fig. 1;

Fig. 6 shows a sectional side elevation view of the antenna feed sub-assembly;

Fig. 7 shows a top plan view of the bottom insulator and printed circuit of the antenna feed sub-assembly of Fig. 6 taken along line 7-7;

Fig. 8 shows an electrical equivalent circuit of the antenna of Fig. 1; and

Fig. 9 shows a side elevation view of another form of the antenna.

Certain general aspects of the invention will be described first. In accordance with the objects of this invention, the antenna of the invention, which may be used for transmitting or receiving purposes or both, has a main radiator element and shunt feed elements at opposite sides of the main radiator element. The antenna elements are preferably of unitary metallic construction in order to achieve maximum mechanical strength. The main radiator element, which is actually the major support of the antenna, is mounted directly on the surface of the vehicle on which the antenna is to be used by means of a base, without the use of any intermediate insulated supports, b ases or housings, thereby avoiding the inherent disadvantages of such insulated members which are brittle, unstable and weak, and are diflicult to attach to the metallic antenna elements.

By using metallic shunt feed elements at opposite ends of the main radiator element, all-metal leading and trailing edges are provided for the antenna, except at the places where the shunt feeds are insulated from the base and main radiator element of the antenna. In the present invention, these places are kept to a minimum size and are filled with a suitable insulating compound. By keeping the use of the insulating compound to a minimum, greater mechanical rigidity of the antenna is obtained.

Since the antenna is used on vehicles moving at high speeds, a swept-back design is utilized and the antenna is generally formed in the shape of an air foil or blade to reduce the drag and thereby increase the maneuverability and flexibility of the vehicle. The overall height of the antenna is made less than a quarter wavelength at the frequency of operation, without changing the range of frequencies of operation, by top-loading the antenna, i.e. having a portion of the top of the antenna main radiator element folded over to be wider than the bottom of the element. This is done without affecting the antennas uniform radiation pattern over the bandwidth of operation.

The symmetry of the radiation pattern of the antenna is further enhanced by employing shunt feeds on opposite sides of the antenna main radiator element, producing a circular pattern like a simple stub antenna, over the whole wide band of operations.

Since the antenna is swept-back, the lengths of the shunt feed elements on each side of the main radiator element are not equal. Further, due to the top-loading, the current distribution along the antennas vertical height is not uniform. Proper current distribution, along the antenna, of the current supplied from the shunt feed elements, is obtained by providing current paths of equal lengths for each of the shunt feed elements. This is accomplished by providing a slot of proper shape and dimension suitably located in the upper portion of the main radiator element. The equal current paths serve to equalize the impedances of the shunt feed elements, thereby mcreasing the frequency bandwidth in which the standing wave ratio is low and improving the power transfer between the antenna and the transmitter or rece ver used in conjunction with the antenna. Also, in this band, the uniformity of azimuthal radiation is improved.

Having thus described certain of the general characteristics of the antenna of the invention, reference is made to the drawings for its structure. Referring to F1gures l5, an antenna is shown comprising a metallic main radiator element 1 having a thick bottom center post 2 and metallic shunt feed elements 3 and 4 on opposite sides of center post 2. The shunt feed elements 3 and are separated from the center post 2 by slots or openings 5 and 6 formed in the main radiator element 1. The shape and size of the main radiator element 1 and HS center post 2 are such that if the shunt feed elements 3 and 4 were removed, the remaining structure would be resonant within the band of frequencies to be matched. As can be seen in Figures 1 and 3, the antenna is toploaded" since the portion of the main radiator element 1 above the center post 2 is in effect folded over at In and 18 substantially wider than the center post 2.

As seen in Figures 1 and 3, the antenna is of a sweptback design with a leading edge 7 (shunt feed element 3) and a trailing edge 8 (shunt feed element 4) which is substantially parallel to the leading edge 7. The sweptback design is utilized to make the antenna a high speed air foil and thus reduce drag. It should be realized that the antenna may be of any shape desired in order to obtain the best aerodynamic characteristics in accordance with the vehicle on which it is used and in the environment in which the vehicle is placed.

The antenna preferably flares out at the lower portrons of center post 2 and shunt feed elements 3 and 4 to form an enlarged base 10, providing extra strength at the mounting location. Center post 2 is preferably integrally formed with the base 10. In one preferred form of the invention, this has been accomplished by casting or machining the base 10 and the antenna elements 2, 3 and 4, as one piece from a suitable goodconductor metal such as aluminum, or an alloy, illustratively A380 of Aluminum Corporation of America. However, the antenna need not be of one piece construction.

A plurality of holes 26) are drilled around the periphcry of the base 10 and accommodate any suitable fastenmg means such as screws 23. The screws 23 serve to mount the antenna on the surface 11 of the vehicle (see Fig. 3).

The bottom portions of the shunt feed elements 3 and 4- are insulated from the base It) at the gaps l3 and 14 at the bottoms of the leading and trailing edges 7 and 8. The gaps 13 and 14 are preferably filled with a suitable plastic insulating compound to insulate the bottoms of the shunt feed elements 3 and 4 from the base 10. Slots 5 and 6 are also filled with the same plastic compound as is another slot 16, in the upper folded-over portion of the main radiator element 1, whose function will be subsequently described. Each of the slots 5, 6 and 16 preferably has a rib extending inwardly on each side of the slot (Fig. 4) to provide a better retention for the plastic insulating compound. These ribs are shown by the dotted lines extending along the slots 6 and 7 in Figure 1.

The plastic insulating compound is preferably a silicafilled epoxy resin such as the product Stycast-2762,

manufactured by Emerson & Cummings Mfg. Company of Canton, Massachusetts. The advantages of this particular epoxy resin compound are as follows: a coefficient of expansion which is approximately equal to the coefiicient of expansion of the metallic elements of the an tenna; low electrical loss properties; negligible deterioration with moisture; an acceptable value of dielectric constant; retention of strength at high temperatures (up to 500 R), which allows the plastic to retain its strength even when the surface of the vehicle and antenna heats up due to frictional effects at high speeds; and erosion resistance. Other suitable insulating materials having similar properties could also be used.

The plastic compound is preferably cast into the gaps 1 3 and 14 and in the slots 5, 6 and 16 and is shaped to conform to the general contour of the antenna body. If desired, the plastic portions on the antenna exterior may be painted with a suitable non-metallic paint to match the metalliecolor of the antenna elements or else the whole antenna may bepain-ted any desired color or coated as desired.

The gaps l3 and 14 between the shunt elements 3 and 4 and the base 10 are kept to a minimum. However, the size should not be so small as to make excessive the capacity which exists between the shunt elements 3 and 4 and the base 10. By keeping the gaps 13 and 14 at the minimum size, less insulation is needed and there fore the antenna is stronger. Attached to and integral with the shunt elements 3 and 4 are tangs 18 and 19 which cross the gaps 13 and 14 and extend into holes in the base 10. Because these tangs extend into the holes in the base 10 and these holes are filled with the same plastic compound as is used to fill the slots 5 and 6 and the gaps l3 and 14- the plastic compound is captured so that when mechanical loads are placed upon the antenna the principal forces experienced by the plastic are compressive. This strengthens the antenna because although the tensile strength of the plastic is much lower than that of metal, its strength in compression is very high. Since the antenna has all-metal leading and trailing edges 7 and 8, except for the small areas 13 and 14 containing the plastic insulating compound, the problem of erosion of the insulation is also reduced. Further, there is less general deterioration of the insulation due to moisture since only a small portion of the insulation is exposed to the atmospheric elements, such as rain, ice, sleet, dust, etc.

The base 10 of the antenna is also formed with a recessed portion 25 (Fig. 3) to accommodate the antenna feed circuit 27 (Figs. 3 and 6), which will be described in detail below. The antenna feed circuit 27 is held in place in the recessed portion 25 of the base 10 by means of a cover or base plate 29 fastened to the base 10 by any suitable means, such as screws 30, and preferably forming a smooth continuation of the bottom of base 10. The screws 30 are located so that they do not con tact the shunt elements 3 and 4 or the conductive portion of the antenna feed assembly 27. The bottom of base 10 and baseplate 29 may be of any suitable shape necessary to conform to the contour of the surface 11 of the vehicle.

Integrally formed as a part of the base plate 29 is a connector 33 which serves to couple the antenna to any suitable transmission line leading to a transmitter or receiver (not shown). The connector 33 terminates in a contact 35, which serves to connect the inner conductor of the transmission line to the conductive portion of the antenna feed assembly '27. While the connector 33 is illustratively shown as a screw-type connector, it should be recognized that any suitable type of connector may be used.

Referring to Figures 6 and 7, the feed circuit assembly 27 comprises top and bottom insulator plates 41 and 42. The insulator plates 41 and 42 are illustratively made of Teflon or other similar insulating material.

Between the top and bottom insulating plates 41 and 42 is a conductive printed or stamped circuit 45, shown in Fig. 7. The circuit 45 is preferably of copper and may be formed on either the upper or lower insulator plate 41 or 42 by any of the known processes such as photo etching, depositing, etc. or may be stamped from a sheet or foil and placed between the insulating plates 41 and 42.

The end of contact 35 is electrically connected to the circuit 45 at point 46 by any suitable means, such as soldering or the like. The curved portion 48 of the printed circuit of Figure 7 is actually an inductance, the purpose of which is to match the antenna to the transmission line. The curvature is not significant, except as it permits the proper length of conductor and hence the proper inductance to be provided between the point 46 and point 51, as will be described.

The circuit 45 is formed with dimpled holes at 50, 51 and 52. Conductive feed rods 54, 55 and 56 are placed respectively in the holes 50, 51 and 52 and are electrically connected to the circuit 45 by any suitable means such as solder. Placed over each of the feed rods 54, 55 and 56 is a respective tubular insulator 59, 60 or 61, shown as generally cylindrical and illustratively made of Teflon or some other suitable insulating material. It should be recognized that the outside of the insulators 59, 60 and 61 need not be cylindrical but may be of any desired polygonal, oval or other configuration.

The center post 2 and the shunt elements 3 and 4 are formed with respective passages or bores 37, 38 and 39, of a suitable diameter and shape to receive insulators 59, 60 and 61 respectively. It will be seen that the bores 38 and 39 start at the ends of the tangs 18 and 19 re spectively, which open into and are accessible from the recessed portion 25 in the antenna base.

As can be seen from Figure 3, the feed rods 54 and 56 and their accompanying tubular insulators 59 and 61 are placed in the respective passages 38 and 39 in the shunt feed elements 3 and 4, while the center feed rod 55 and its accompanying tubular insulator 60 is placed in the passage 37 of the center post 2. The feed rods 54 and 56 act as capacitors and in conjunction with the inner surfaces of bores 38 and 39 surrounding them, and in effect, the shunt feed elements 3 and 4 are coupled to circuit 45 by respective series capacitive feed arrangements.

A shorting cap 63 is connected to the center feed rod 55, and the ends of the shorting cap 63 are clamped around the tubular insulator 60. When placed in the passage 37, the shorting cap 63 makes contact with the center post 2 and causes center feed-rod 55 and passage 37 eifectively to act as a short-circuited coaxial line section forming a parallel resonant circuit. The length of the center rod 55 determines the position of the shorting cap 63 and hence the resonant frequency of the tuned circuit. The length of the feed rod 55 and therefore the resonant frequency of the effective tuned circuit, is so chosen as to obtain the best overall results for the antenna.

To insure that the current from each of the two shunt feed rods 54 and 56 travels equal paths in the radiator element 1, and to provide thereby a substantially uniform current distribution between the two elements 3 and 4, slot 16 is formed in the upper section of the main radiator element 1. The exact location and shape of the slot 16 is determined experimentally to obtain the widest band width, most symmetrical radiation pattern, and lowest standing wave ratio. Among the criteria which are considered in the choice of the shape and location of the slot are: to place it at or near the center of the top regio'n above the center of the base 16, to get maximum area for top-loading eifect, and to maintain the maximum mechanical strength of the antenna. the mechanical strength of the antenna, it is desirable To maintain to make the slot 16 as narrow as possible. However,

the slot 16 should not be made so narrow that shorting of the antenna current occurs due to the capacitive effect between the opposite edges of the slot. The general shape, curvature and location of slot 16 as shown in Figs. 1 and 3 have been found advantageous. The slot 16 also is preferably ribbed as shown at Fig. 4.

In providing the slot 16, the impedances of the shunt feed elements 3 and 4 tend to become equalized due to the equalization of the current paths of the feed elements 3 and 4. By making the impedances of the shunt feed elements 3 and 4 equal, the maximum standing wave ratios of the antenna are reduced in the operating frequency band. In one antenna which has been built, utilizing a slot shaped similar to the slot 16 shown in Figures 1 and 3, a maximum standing wave ratio of 2.521 for an antenna operating in the range of frequencies from 225400 megacycles has been obtained. At the center frequency of operation, approximately 312 megacycles, the standing wave ratio was in the order of 1.2:1.

Figure 8 shows an electrical equivalent circuit of the antenna of Figures l-5. Referring to Figure 8, and considering use of the antenna in a transmitting mode of operation, the antenna receives its energy from a transmission line 68 having an inner conductor 69. This line is coupled to coupling 33 of Fig. 3. The inner conductor 69 of the transmission line terminates into an inductance 48' which is the curved portion 48 of the circuit 45 of Fig. 7. It should be realized that at lower frequencies of operation the circuit inductance 48, may be replaced by an actual physical coil. The end of the inductance 48', opposite the transmission line, branches into three circuits. These circuits comprise series capacitors 70 and 71 at the ends of respective transmission line sections 91, 92 and the parallel resonant circuit represented by capacitor 72 and inductor 73.

Physically, the capacitors 70 and 71 are formed by the feed rods 54 and 56 and their accompanying tubular insulators 59 and 61, in association with the surrounding metal body of the radiator element. As previously explained, the feed rods 54 and 56 and their insulators serve to series capacitively feed the shunt elements 3 and 4 of the antenna. The tuned resonant circuit comprising capacitor 72 and inductor 73 is physically the center feed rod 55 and its accompanying tubular insulator 60 and shorting cap 63 in association with the surrounding metal body. The main radiator element 1 is connected to ground, at the base 10, and the resonant unit 7273 is therefore in shunt between point 51 and ground. The length of the rod 60 is desirably chosen so that the parallel resonant circuit is resonant at a point near the highest frequency of the band of operation of the antenna. The design evolved may be considered a fiat stub, grounded at the center of the base and fed by two shunt elements.

The effect of the various parameters can best be explained by visualizing standard antenna impedance diagram in which the first and fourth quadrants of the diagram respectively represent inductive and capacitive reactance and the line of the abscissa, between the first and fourth quadrants, represents a pure resistance. If the impedance of the antenna is plotted for various values of operating frequencies, the result is an impedance curve. Addition of the parallel tuned resonant circuit 72, 73 has the effect of making the impedance diagram curve of the antenna shift from the capacitive reactance portion (fourth quadrant) upward towards the abscissa, which is the pure resistance line. Optimization of the ratio of the inductance of the coil 48 and the capacitor 72 serves to tighten up the impedance curve, i.e. decrease its excursions into the inductive and capacitive reactance portions (first and fourth quadrants). Increase or decrease, in the value of the series feed capacitors 7t 71 serves in large part to rotate the impedance curve about its own center, thereby helping determine at what frequencies the impedance of the antenna is purely resistive. By suitably selecting resonant circuit 72, 73, inductance 4S, and capacitors 70 and 71, the impedance curve can be made to center around the pure resistance line at a desired value of resistance and remain near that value over a substantially wide band width without extending too far into the reactive regions. This means that the antenna will have a good standing wave ratio and will present a good match to the transmission line over a broad band of operation.

Utilizing the design principles of the antenna of the present invention, one embodiment has been constructed which has all of the aforementioned desired electrical and mechanical characteristics while operating in the frequency range of 225-400 megacycles and at speeds in the range of mach 1.5-2.5. By the use of the present type of top-loading, and feeding, the overall length of the antenna has been reduced approximately 20% from the length of a quarter wavelength stub at the center frequency of operation.

Below a frequency of approximately 270 megacycles, with an antenna of the dimension of the above example, it is not necessary to use shunt feeds at opposite sides of the center post 2 in order to obtain a symmetrical radiation pattern. At these frequencies, one of the shunt feed elements may be eliminated and a single shunt feed may be used with a slot, similar to slot 16, to shape the path of current distribution from the feed element. The antenna of Figs. 1-8 may be modified to a single shunt feed type by removing one of the feed rods 54 or 56 from one of the respective shunt elements 3 or 4, while still retaining the slots 5 and 6 and the gaps 13 and i4, filled in with the insulating compound. As an alternative arrangement, one of the feed rods 54 or 56 may be removed and the shunt element, from which it was removed, made integral with the center post 2 and the base 10 by eliminating the proper slot 5 or 6 and making its space of metal. In this arrangement, the adjacent gap 13 or 14 and the corresponding passageway 33 or 39, of the feed element from which the feed rod was removed, would also be of metal and be integrally formed with the base 10.

Another type of antenna of the single shunt feed type is shown in Fig. 9 where those parts of the antenna which are the same as those in the antenna of Figures 1-8 have been designated by the same reference characters. Referring to Figure 9, an antenna is shown with leading and trailing edges 7 and 8 being swept back at a greater angle than the antenna of Figures 1 and 3. Such a greater angle permits the antenna to be used at higher speeds. The antenna of this embodiment is more toploaded and is of smaller overall length in proportion to a quarter wavelength, at the lower, center frequency of operation, than the antenna of Figs. 1-5.

The antenna consists of a main radiator element 75 integrally formed with a base 10, and with a gap '77 and apertures '78 and 79. The metallic portion $1, formed by the gap 77 and the opening 78, comprises the single shunt feed element of the antenna. The shunt feed element 81 may be supplied energy by a feed circuit assembly similar to that shown in Figures 3, 6 and 7.

A slot 32 is also out in the main radiator element 75 at a point above the opening 79. The slot 82 serves the same purpose as slot 16 shown in Figs. 1 and 3, namely to provide top loading without altering the desirable aerodynamic shape, and to insure a desirable current distribution to or from the shunt feed element 81. As in the above described embodiment of the invention, the shape and location of the slot 82 is experimentally determined and is so placed and shaped so as to give the best overall results. The antenna shown in Fig. 9 may be converted into a double shunt fed type, similar to the antenna shown in Figs. 1-8, by extending the trailing edge 8, below the slot 82, downwards and feeding it by means of a suitable arrangement similar to the one shown in Fig. 6.

Also, as in the case of the antenna of Figures 1-8,

the gap 77 and the openings 78, 79 and 82 are preferably filled with a suitable insulating compound, such as that described above. As is seen in Figure 9, the leading edge 7 and the trailing edge 3 of the antenna have only small areas of insulation. This provides for greater structural strength and solves the problem of rain erosion, i.e. deterioration and weakening of the insulation by moisture and abrasion.

Therefore, it is seen that a novel antenna has been disclosed, suitable for use on vehicles moving at high velocities, and which is structurally strong, due to its limited use of insulation and by making its main radiator support integrally formed with the base of the antenna and by its tapered cross-section along its height with the greatest section at the base to provide best cantilever support action. The base is fastened directly to the surface of the vehicle without the use of any insulating members. By suitable location and shaping of a slot 16 in the main radiator element of the antenna, a current distribution pattern is obtained for the antenna which insu-res a low standing wave ratio and symmetry of the radiation pattern. By top-loading the antenna and feeding in the manner described a substantial reduction in size is obtained.

While several forms of antenna have been shown and described, consisting of several specific shapes, it should be recognized that the present invention is not limited to such sizes or shapes nor would the antenna be limited to use at any particular frequency or band of frequencies. Many antennas of various descriptions could be constructed utilizing the principles of the present invention.

While preferred embodiments of the invention have been described above, it will be understood that these are illustrative only, and the invention is limited solely by the appended claims.

What is claimed is:

1. An antenna for high speed vehicles comprising a conductive air foil having a body portion and a base adapted to be mounted on and electrically connected to said vehicle, said body portion extending sl-antedly upward from said base and tapering in cross section away from said base, said body portion also having an air foil cross section with low aerodynamic drag and with a leading edge and a trailing edge, said body portion having a pair of slots, each extending upwardly from said base and generally along but spaced from a respective edge, each of said edges having a gap adjacent said base and communicating with a respective slot, a tang attached to and integral with each of the portions of said body between said edges and said slots, each of said tangs extending across each of said gaps and into a respective hole in said base, a bore formed within said body portion between each of said edges and its adjacent slot, said bore beginning in the tang of said body portion, a respective conductor insulatedly supported within each said bore and forming a capacitance therewith, said body portion also having a bore formed therein extending upwardly through said base between said slots, a conductor mounted substantially coaxially within said latter bore and conductively connected to said body portion at the end of said conductor within said latter bore to form a short-circuited transmission line section forming a resonant circuit, said base having a hollow portion communicating with all said bores, a flat conductive plate insulatedly mounted in said hollow base portion, said plate having a plurality of strips extending from a common junction point, said capacitor conductors being electrically connected to respective ones of said strips substantially equidistant from said junction point and said resonant circuit conductor being directly connected to said plate at said junction point, a transmission line connector connected to another one of said strips, and an inductance interposed between said connector and said junction point in series with said latter strip, said body portion further having a slot extending inwardly from an intermediate portion of said trailing edge to provide an eifective folded top-loading section for said body portion without increase in height of said antenna, said slot being arcuately curved inwardly of said trailing edge and away from said base, with an end substantially directly above the section of said body portions between said first pair of slots.

2. An antenna for high speed vehicles comprising ,a conductive air foil having a body portion and base adapted to be mounted on and connected electrically to said vehicle with said body portion slanted with respect to the surface of said vehicle to provide lowered aerodynamic resistance and form slanted leading and trailing edges, said body portion having a pair of slots, each extending upwardly from said base and generally along but spaced from a respective edge, each of said edges having a gap adjacent said base and communicating with a respective slot, a tang attached to and integral with 'each of the portions of said body between said edges and said slots, each of said tangs extending across each of said gaps and into a respective hole in said base, and means for coupling an energy conductor toeach of said edges at the side of its respective gap opposite said base, said coupling means comprising a bore formed within said body portion between each of said edges and its adjacent slot, said bore beginning the tang of said body portion, a respective conductor insulatedly supported within each said bore and forming a capacitance therewith, and

said conductor within said latter bore to form a shortcircuited transmission line section and a further line section within said base and connecting said first capacitor conductors and said latter conductor.

3. An antenna for high speed vehicles comprising a conductive air foil having a body portion and base adapted to be mounted on and connected electrically to said vehicle with said body portion slanted with respect to the surface of said vehicle to provide lowered aerodynamic resistance and forming slanted leading and trailing edges, said body portion having a pair of slots, each extending upwardly from said base and generally along but spaced from a respective edge, each of said edges having a gap adjacent said base and communicating with a respective slot, and means for coupling an energy conductor to each of said edges at the side of its respective gap opposite said base, said coupling means comprising a bore formed within said body portion between each of said edges and its adjacent slot, a respective conductor insulatedly supported within each said bore and forming a capacitance therewith, and a transmission line coupling coupled to each of said conductors.

4. An antenna for high speed vehicles comprising a conductive air foil having a body portion and base adapted to be mounted on and connected electrically to said vehicle with said body portion slanted with respect to the surface of said vehicle to provide lowered aerodynamic resistance and forming slanted leading and trailing edges, said body portion having a pair of slots, each extending upwardly from said base and generally along but spaced from a respective edge, each of said edges having a gap adjacent said base and communicating with a respective slot and means for coupling an energy conductor to each of said edges at the side of its respective gap opposite said base, said body portion further having a slot extending inwardly from an intermediate portion of said trailing edge to provide an efiective folded top-loading section for said body portions without increase in height of said antenna, said slot being arcuately curved inwardly of said trailing edge and away from said base, with an end substantially directly above the section of said body portions between said first two slots.

5. An antenna for high speed vehicles comprising a conductive air foil having a body portion and base adapted to be mounted on and connected electrically to said vehicle, with said body portion slanted with respect to the surface of said vehicle to provide lowered aerodynamic resistance and forming slanted leading and trailing edges, said body portion having a pair of slots,

each extending upwardly from said base and generally along but spaced from a respective edge, each of said edges having a gap adjacent said base and communicating with a respective slot, and means for coupling an energy conductor to each of said edges at the side of its respective gap opposite said base, said body portion further having a slot extending inwardly from an intermediate portion of said trailing edge to provide an effective folded top-loading section for said body portion without increase in height of said antenna.

6. An antenna for high speed vehicles comprising a conductive air foil having a body portion and base adapted to be mounted on and connected electrically to .said vehicle with said body portion slanted with respect to the surface of said vehicle to provide lowered aerodynamic resistance and forming slanted leading and trailing edges, said body portion having a pair of slots, each extending upwardly from said base genenally along but spaced from a respective edge, each of said edges having .a gap adjacent said base and communicating with a respective slot and means for coupling an energy conductor to each of said edges at the side of its respective gap op-po site said base.

said vehicle, said body portion having an edge extending .upward from said base and having a slot formed in said body portion extending upwardly from said base and generally along but spaced from said edge, said edge having -a gap adjacent said base and communicating with said .slot, and means for coupling an energy conductor to said edge at the side of said gap opposite said base, said coupling means comprising a bore formed within said body between said edge and said slot and a conductor insulatedly supported within said bore and forming a capacitive coupling, said body portion also having a bore formed therein extending upwardly through said base, and said coupling means further comprising a conductor mounted substantially coaxially within said latter bore and conductively connected to said body portion at the end of said conductor within said latter bore to form a shortcircuited transmission line section, and a further line section within said base and connecting said first capacitor conductor and said latter conductor.

8. An antenna for high speed vehicles comprising a conductive air foil having body portion and a base adapted to be mounted on and electrically connected to said vehicle, said body portion having an edge extending upward from said base and having a slot formed in said body portion extending upwardly from said base and generally along but spaced from said edge, said edge having a gap adjacent said base and communicating with said slot, and means for coupling an energy conductor to said edge at the side of said gap opposite said base, said coupling means comprising a bore formed within said body between said edge and said slot and a conductor insulatedly supported within said bore and forming a capacitive coupling.

9. An antenna for high speed vehicles comprising a conductive air foil having a body portion and a base adapted to be mounted on and electrically connected to said vehicle, said body portion having an edge extending upward from said base and having a slot formed in said body portion extending upwardly from said base and generally along but spaced from said edge, said edge having a gap adjacent said base and communicating with said slot, and means for coupling an energy conductor to said 1 1 edge at the side of said gap opposite said base, said body portion further having a slot extending inwardly from an intermediate portion of a body portion edge opposite said first mentioned edge to provide an efiective folded top-loading section for said body portion without increase in height of said antenna, whereby for a given range of operating frequencies said antenna has reduced height.

10. An antenna for high speed vehicles comprising a conductive air foil having a body portion and a base adapted to be mounted on and electrically connected to said vehicle, said body portion having edges extending upward from said base and having a pair of slots formed in said body portion, said slots extending upwardly from said base and, generally along but spaced from a respective edge, each of said edges having a gap adjacent said base and communicating with a respective slot, and means for coupling an energy conductor to said edges at the side of said gaps opposite said base.

11. An antenna for mounting on a conductive surface comprising a conductive base portion adapted to be secured to said surface and a conductive body portion extending away from said base portion, said body portion having a cutout portion adjacent said base and at one edge of said body portion to form a feed point, and means coupling an energy conductor to said feed point comprising a bore within said body portion, adjacentsaid feed point, a conductor insulatedly supported within said bore to form a capacitor therewith, and transmission line means within said base coupled to said conductor, said base having a hollow portion and said transmission line means comprising a flat conductive plate insulatedly mounted in said base hollow portion.

12. An antenna for mounting on a conductive surface comprising a conductive base portion adapted to be secured to said surface and a conductive body portion extending away from said base portion, said body portion having a cutout portion adjacent said base and at one edge of said body portion to form a feed point, and means coupling an energy conductor to said feed point comprising a bore within said body portion adjacent said feed point, a conductor insulatedly supported within said bore to form a capacitor therewith, and transmission line means within said base coupled to said conductor.

13. An antenna for mounting on a conductive surface comprising a conductive base portion adapted to be secured to said surface and a conductive body portion extending away from said base portion, said body portion having a cutout portion adjacent said base and at one edge of said body portion to form a feed point, and means coupling an energy conductor to said feed point, said body portion having a curved slot extending inwardly from one edge thereof and curving away from said base to form a folded top-loading section without increase in height.

14. An antenna for use on the surface of a vehicle comprising a metal body having a first slot forming a metallic main radiator element and a metallic shunt feed element on one side of said main radiator element, means for electrically and mechanically connecting the base of said main radiator element to said surface, means for supplying energy to said elements, each of said elements being formed to accommodate said energy supplying means therewithin, said main radiator element extending above said feed element and having a second slot separate from said first slot forming a folded-over top-loading portion and controlling the path of energy flow on said elements, insulation in each of said slots shaped to the contour of said antenna, and further insulation placed to insulate only said shunt feed element from said vehicle surface.

References Cited in the file of this patent UNITED STATES PATENTS 2,507,528 Kandoian May 16, 1950 2,557,951 De Rosa et a1 June 26, 1951 2,614,219 Cary Oct. 14, 1952 2,826,756 Cary Mar. 11, 1958 FOREIGN PATENTS 125,006 Sweden May 24, 1949 

